Unformatted text preview: al energy changes of water, and take the specific volume
of water to be 0.001 m3/kg. Answer: 2100 kPa
P2 PUMP
10 kW
100 kPa FIGURE P7–82
7–83E Saturated refrigerant134a vapor at 20 psia is compressed reversibly in an adiabatic compressor to 120 psia. Determine the work input to the compressor. What would your
answer be if the refrigerant were first condensed at constant
pressure before it was compressed?
7–84 Consider a steam power plant that operates between the
pressure limits of 10 MPa and 20 kPa. Steam enters the pump
as saturated liquid and leaves the turbine as saturated vapor.
Determine the ratio of the work delivered by the turbine to the
work consumed by the pump. Assume the entire cycle to be
reversible and the heat losses from the pump and the turbine
to be negligible.
7–85 Reconsider Prob. 7–84. Using EES (or other)
software, investigate the effect of the quality of
the steam at the turbine exit on the net work output. Vary the
quality from 0.5 to 1.0, and plot the net work output as a function of this quality.
7–86 Liquid water at 120 kPa enters a 7kW pump where its
pressure is raised to 3 MPa. If the elevation difference betw...
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 Spring '09
 Thermodynamics, Energy, Entropy, entropy change

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